US, UK and Australian citizens are in the same position. You simply have to show international transfers of 65k per calendar month for the preceding twelve months.
Lost investment income on the 800,000 baht. Perhaps also include calculations for the 65k/month method. Also any agent fees are discretionary. Most people do their own extensions and online 90-day reporting.
Yash Arora. I'm not familiar with the "married to a Thai" conditions, as there are variations. For example, you can obtain a work permit and use your salary to satisfy the 40k conditions. I suggest you post your questions to the Thai visa advice group, and you will get a very comprehensive answer