I got my Thai tourist visa at the Hanoi embassy two weeks ago. Yes, you need a proof of accommodation for your whole stay in Thailand - I booked a hotel on Agoda for 40 days and paid for it, then after my visa was approved, I canceled it and got refunded.
The whole process in Hanoi was very smooth and quick - took about 3 days for them to grant me the visa, they were very helpful at the embassy and basically told me exactly what to do.