Are you referring to the month of August? Sunday is the 28th. Anyways, I assume you meant that you don't want to spend $70 per night, right? I have three suggestions:
1) Golden House VIP House on Chitlom. Shopping all around plus a good massage place beside it.
2) Kingston Suites on Sukhumvit
3) Paradiso Boutique Hotel, also on Sukhumvit
All three are close to the skytrain.