While some like to do the American thing and split the bill, why not just go to these places where you can pay one price and then booze it up until you pass out? Repeat as MUCH as you like.

Akiyoshi

It’s neither bar nor a topnotch hotel hangout but just another Japanese restaurant in Mango City. However, with the irresistible deal of B199 daily, you are free to gorge yourself on as much draught Heineken, Singha and of course Asahi as you can from opening until closing (Mon-Fri 11am-2pm, 5:30-10pm. Sat-Sun and public holiday 11am-10pm). Lets enjoy wasabi and beer this weekend, then.
1521/1 Sukhumvit Rd., between Soi 67 and 69, 02-381-2267/-8.

Unicorn 70’s Bar

Sitting in a small sub soi off Khao San is Unicorn, which originally targeted the boy-on-boy market but not anymore. For B199, you can get free flow draught beer from 7-10pm daily while Mr. DJ and the bands entertain you with indie pop, rock and of course, coyote dancers.
164 Khao San Rd., 02-281-2366. Open daily 7pm-1am.

Zuk Bar

How about starting off the night with a little wine? Free flow, that is. Hmm… that could mean one heck of a sloppy evening, but hey, be that posh dude you know you are and head over to Zuk Bar. This elegant yet intimate setting allows you to gaze over a lotus ponds while you sip a choice of seven brands of reds and whites. Gather some friends together and chat like civilized beings. B1,000 from 5:30-8pm daily.
Sukhothai Hotel, 13/3 South Sathorn Rd., 02-344-8888. Open daily 6pm-1am.