“Koay teow” (as it’s called in Penang) is “guo tiew” (粿條), the flat rice noodle of the “Chaozhou” (潮州) people. In Thailand, it’s sometimes spelt “kueh teow” when written in English. The “Chaozhou” is spelt “Teochew” in Singapore & Malaysia, and “Taechiu” in Thailand, but are the same people. In Teochew/Taechiu dialect, they’d call each other “ga gi nang” (自己人), i.e. “our people” - often used by the “Chaozhou” diaspora in South-East Asia. They form the majority of Chinese in Thailand and Indo-China, so one can get by speaking Teochew to ethnic Chinese in Bangkok, Ho Chi Minh City or Phnom Penh. The Teochews are the second-largest Chinese-dialect group after the Hokkiens in Singapore and Penang (not so much in Kuala Lumpur or Ipoh which are mainly Cantonese & Hakka). Street/hawker food in Singapore and Penang are very much influenced by the Teochews, e.g. “char koay teow”, “kway chiap”, “chwee kueh”, “soon kueh”, etc. The Teochews like clear soups, shellfish like cockles & crabs, and has a lighter (blander?) cuisine than the neighbouring Cantonese and Hokkiens.
The “Teochew” dialect is also very similar to “Hokkien”, which is spoken in Singapore and Penang, as by the Chinese in Indonesian cities like Jakarta, Surabaya, Medan, etc. and also the Chinese in Manila & other cities in the Philippines.
Cuisine-wise, “Teochew” cuisine influence the street foods of Singapore, Penang, Bangkok, Ho Chi Minh City, etc., though some level of indigenization takes place, e.g. sweeter in Thailand and Vietnam where locals have a sweet tooth.
In Vietnam, the popular “Hu Tieu Nam Vang” (literally translated as “Koay teow Phnom Penh”, as the dish was introduced to the Vietnamese by itinerant Teochew noodle vendors who resettled from Cambodia) are 90% similar to Penang “koay teow th’ng”. Ditto Vietnamese “banh uot”, which is known as “chee cheong fun” in Singapore & Penang. In the case of “banh uot”, the dressing is sweeter, whilst “banh uot dac Biet”, i.e. the special version will see the noodle dish garnished with various forms of Vietnamese “charcuterie”, a result of French culinary influence on Vietnamese cuisine, whereas “chee cheong fun” in Penang incorporates local “hae koh” (fermented shrimp paste) indigenous to the place, but which is not used in Singapore & Bangkok which use hoisin sauce.
Singaporean/Malaysian “chwee kueh” is spelt “jui guay” in Thailand, but pronounced the same way in Teochew dialect. In Vietnam, it’s called “banh beo”, but is essentially the same dish.
Singaporean “chwee kueh” from Jian Bo, Tiong Bahru Food Centre:
Penang “chwee kueh” from Chew Jetty, Weld Quay:
Bangkok “jui gway” from Yaowarat morning market:
Vietnamese “banh beo” from Ho Chi Minh City’s Cho Binh Tay, Chinatown:
Back to your question of the difference between Penang “koay teow th’ng” and Thai “kueh teow” soup - the Thai version will be served with additional condiments on the side like sugar, fish sauce (“nam pla”), red chilli flakes, vinegar and light soy-sauce (the Thais call this selection of condiments “puang” & you’ll see this on tables most Thai restaurants) , whereas the Penang version will be served with cut red chillis in soysauce - Penangites, like other Malaysians and also Singaporeans, use very little fish sauce as a condiment or in their cooking, compared to the Thais and Indo-Chinese. Else, the two dishes (Penang vs Bangkok) are almost similar.
Penang’s duck-meat “koay teow th’ng” retains its Teochew roots with a clear, if flavoursome soup-base, whereas its Thai counterpart, the “kueh teow ped” has a darker coloured soup through addition of soy-sauce, oyster sauce and fish sauce during the cooking phase, and has a deeper, more mellow taste. But the flat rice noodle used is the identical.
Some noodle names in Singaporean/Penang Hokkien-Chinese versus the Thai terms:
- Koay teow = kueh teow
- Bee hoon = sen mee
- Cho bee hoon = sen lek
- Tua pan koay teow = sen yai
- Hokkien mee = mee leuang
- Tunghoon = woonsen