AS Seoul seeks to woo tourists as part of Visit Korea Year, those from Hong Kong cannot expect the same welcome mat. While most foreign travellers from March will be able to breeze through Korea's streamlined Customs procedures in seconds, flights from Hong Kong, Thailand and other Golden Triangle drug producers will be viewed with suspicion. ''These countries are regarded as key transit centres for drug couriers,'' according to a source at Korea's Drug Enforcement Department at Seoul's Kimpo International Airport. ''We are on the alert as there have been many Hong Kong Chinese caught bringing drugs into the country, particularly in 1992.'' The official said that all passenger lists for flights from Hong Kong and Thailand would come under close scrutiny. But he stressed that ''ordinary Hong Kong passengers'' would be processed in the same manner as other foreign visitors. ''We would have to have a reason for being suspicious before we apprehended any traveller from Hong Kong.'' A Hong Kong businessman based in Seoul said: ''This is discrimination against Hong Kong people. The Hong Kong Government must launch an official protest.'' The English-language Korea Times quoted Korea Customs Administration officials as describing Hong Kong and Thailand as ''crime prone and narcotics-producing areas''. Customs agents will make a random interview with ''suspicious inbound'' travellers although it will minimise physical inspection, the paper said. When approached, Customs officials said statistics to back up Hong Kong's so-called crimewave were not available. Ironically, Hong Kong, with the number of visitors soaring by 96 per cent last year, has been one of Korea's few success stories on the tourism front. Since the dropping of the visa requirement for Hong Kong Chinese, to coincide with the hosting of the Taejon Expo last year, there has been a steady stream of visitors, especially for skiing.