Ive lived in SE Asia for a while now and Bangkok is still the best City. Closely rivaled by HCMC.
If you think Bangkok should be on the list I assume you've never been to Indonesia or Malaysia
Lived in Malaysia for over a year and have been to Indonesia a number of times (although Jakarta nearly made the list, it has to be said). Lived in Vietnam for 5 years too and agree with HCMC which pisses all over Bangkok imo, as does Hanoi, Phan Thiet, Dalat, Vung Tau, Nha Trang, Can Tho, Yangon, Phnom Penh, Singapore, Jahor Baru, KL, Alor Setar, Kangar, Ipoh, Georgetown, Songkhla, Phukett, Hat Yai, Manilla, Cebu, Tagbilaran and a plethora of other cities in SE Asia (apologies for any spelling mistakes in all that lot). It is, of course, only mt opinion though.