Do I need to show financial stability for a DTV visa as a spouse in Thailand?

Need your own money regardless for the visa , doubt be approved without any funds

Obviously you have to wait until you are married but it's worth checking with the consulate you plan to use to see if you have to be married for a certain amount of time before you can apply. I don't know how consulates treat this but some immigration offices inside Thailand won't give you a marriage visa until you have been married 2 months. As to whether your then husband can provide you with a sponsorship letter it will likely depend on how much money he can show in his bank account

Some embassies is okay with letter. But if he only have 500k then i dont think they will aprove. So depends on his financials i think. Hard to say aswell since all embassies are diffrent

You need your own money on your bank account, some embassies might accept a sponsor letter but perhaps you should mail them first and figure out if that could be an option