Security issues, Kampuchea, fighter planes, and perhaps refugees are likely to overshadow economic development when Thailand's prime minister, Prem Tinsulanonda, visits Washington today.
The main item on the agenda when General Prem meets President Reagan will probably be the recent fighting on the Thai-Kampuchean border. In the last few weeks, Thai aircraft and artillery have once again engaged Vietnamese troops who crossed into Thailand in pursuit of Khmer Rouge guerrillas.
The fighting underlines Thailand's claim to be the frontline state of the six-member Association of Southeast Asian Nations (ASEAN). It probably also intensifies the Thais' belief that they should be receiving more political and material support from the United States in its confrontation with Vietnam, whose troops currently occupy Kampuchea (Cambodia).
Like the other ASEAN countries, Thailand feels that the US has had long enough to recover from its ''Vietnam syndrome,'' which has left it with an abiding reluctance to play an assertive role in Southeast Asia.
The US says it is content to follow ASEAN's lead on the Kampuchea issue. ASEAN is unimpressed by this deference.
But, a Thai official recently noted, the US does not always follow the lead. ASEAN has frequently asked the US to provide open support for the anti-Vietnamese Coalition Government of Democratic Kampuchea, composed of the Khmer Rouge and the noncommunist factions of Prince Norodom Sihanouk and Son Sann. The US has so far avoided doing so.
The Thais will probably try again to get the US more actively involved. Shortly before General Prem left on his tour, officials here were quoted as saying they wanted ''tangible political commitments'' from Washington over the Kampuchea issue.
The recent fighting will also probably give the Thais an advantage in driving home another key item on their agenda: their request to buy a squadron of highly sophisticated and expensive F-16 fighter jets.
The US has been cool to this idea, too. It seems to feel that Thailand does not really need such an advanced fighter. It also apparently feels that the planes would strain Thailand's financial resources and technical capacities. The F-16s, excluding spare parts, would cost about $500 million, and would be difficult to maintain.
Washington is also probably afraid that demand for the F-16s may snowball if it grants Thailand's request. The Philippines and Indonesia have already asked to buy the planes, and Singapore might eventually follow suit.
Thailand is undeterred. Bangkok has brushed aside a US suggestion that it buy a cheaper and less sophisticated export model of the F-16, the F-16/79. The Thais say they need the advanced model to deal with the MIG-23s they expect the Vietnamese to receive soon from the Soviets.
The F-16 deal is now coming to be seen as a test of US friendship and commitment to Thailand's security. And, perhaps most important, it seems to have become a special interest of the Army's supreme commander, Gen. Arthit Kamlang-ek, whose political prominence seems often to overshadow that of General Prem.
If pressed for further proof of their commitment to Thailand, US officials will probably point to the size of the US military assistance program, the second largest in east Asia. For fiscal year 1985, the Reagan administraion is requesting $105.4 million.
One area of the aid program, however, has been an occasional source of friction: refugees and piracy.
Thailand feels it does not receive sufficient recognition for its role as country of first asylum to Indochinese refugees. It considers the rate of refugee resettlement in the West much too slow, and is extremely sensitive to any criticism of its refugee policy.
For its part, the US is concerned at the lack of success of a joint United Nations-Thai government piracy program. The program is supposed to suppress the pirates who prey, often with extreme brutality, on refugee boats in the Gulf of Thailand. As of February, however, US Assistant Secretary of State Paul Wolfowitz noted, the program had not caught any pirates.
The criticism apparently stung the Thais, who were already angered at a UN High Commissioner for Refugees protest over an incident in which Thai officials allegedly pushed two refugee boats back to sea, resulting in at least 32 deaths.
The Thai government said the UNHCR report was unsubstantiated. Soon afterward the head of Thailand's National Security Council, squadron leader Prasong Soonsiri, described the funding for the anti-piracy program as ''chickenfeed.'' He hinted the program may soon be stopped.
Because a large part of Prem's entourage is made up of economic specialists, businessmen, and bankers, it will be more concerned with obtaining support for major Thai development projects. It is likely to push for a plan to develop Thailand's eastern seabord, a program estimated to cost at least $4 billion.
This and other large development projects have moved at a gentle pace under Prem.
His four years in office have been a time of relative stability but little dynamism. An unassuming and apparently shy career soldier, Prem was reportedly very close to the royal family when he took office in 1980.
The subtle but clear support of the royal family proved vital the following year. On April 1, 1981, a group of young colonels staged a coup. The officers, known as the ''Young Turks,'' were impatient with the slow pace of economic and social change in Thailand and demanded swift reforms.
Prem and the royal family took up residence in a provincial capital and the coup fizzled. With the collapse of the coup, paradoxically, Prem lost much of his influence.
The Young Turks had been the firmest element of his own power base. They had even asked him to lead the coup.
Afterward, another senior officer, General Arthit, began his rapid ascent. Now supreme commander of the Thai armed forces, General Arthit is thought to be the most likely successor when Prem leaves office.
Prem will visit six nations - Canada, the US, Denmark, Yugoslavia, Switzerland, and West Germany - before returning to Bangkok on April 27.