OK, here's some review for CANTON house at Central Festival 6th floor. Have posted pics of uneaten food. This is the closest Cantonese food you can get in Sin City. Price is quite cheap and place is clean. Only thing is there are quite a number of dishes from the menu they don't serve when near the closing hours. You can also get good Dim Sum here. Think the whole dinner was around THB 1200. Have to deduct THB 200 from the bill because of the 2 bottles of Heineken beer.
Cantonese food is quite easy to find in Bangkok and south. Dimsum and wanton mee (basic and classic Cantonese fares) are quite popular around. Ratna is also a Thai version of Cantonese Horfun. Surprisingly, there're almost no Thai Cantonese I see in Thailand, most of Thai Chinese I see are Thai Teochew.