Good advice posted already but in case you were thinking of it DO NOT transfer a lump of money to her. They frown on this and it will count against you. My wife doesn't work (looks after the kids) so we just show her real bank account as it is (pretty empty), but all my supporting financials - no problem.
You are the sponsor so they are only interested in your financials, not hers, they just need to know she will return to Thailand - your marriage, non immigrant visa, and the houses in her name are good.
Also write a good cover letter from you explaining your relationship, life and commitments in Thailand, reasons to come back, certify you will cover all expenses during the trip, and give a brief explanation of why you're going (to visit family etc).
Cover all that and you should be fine but as others have warned, get on with it!