You don't need 400k baht in a Thai bank if you apply for a thai spouse visa at a Thai embassy. You need them in case that a. you extend it for one year (need at least 2 months seasoning) or b. you come to Thailand under Visa exemption/transit Visa and you do Visa status alteration at your immigration office (must file a TM86 or TM87)
As long as you have the financial requirements (800k baht in a Thai bank account or monthly income of at least 65k baht) there should be no remarkable difference among the 2 nationalities
If anything else fails, go and book a hotel room for one night. Ask the staff to hand you the tm30 report slip. You need tm30 only for extensions of visa and 90 days report anyway.
Looks like multi entry non O is your best option. It's valid for one year but you have to do a border run every 90 days. No financial proof required. You can go apply in Savannaket or Ho Chi Minh