Anonymous participant 179 many things are not required but it seems from people's experiences here, more is better. Also I have no reason to believe my agency would ask me to give them double the documents just for fun when they told me clearly if I went to Laos I would only need to submit 3 months.
I am working with an agency and applying to Hanoi. They had me submit 6 months of invoices totaling min 3kusd per month, 6 months of my bank account showing the same invoices being deposited, they had me move money from my savings account (which is labeled as a brokerage account at my bank) to my checking account. I also submitted a summary of all of my accounts with balances and last 4 of my account numbers so they could see that the money has been in my accounts for 6 months. They told me Vietnam wants 6 months of docs, if I had applied in Laos it would be 3.
Talk with compass visa. They've done mine and a friend's. You can do a consult for free and tell them your situation. They'll recommend what's best and where to apply, how long etc. You pay only if you want them to look over and handle all your paperwork. Very professional. You can DM me if you have specific questions about my experience.
I paid them 5000thb which seems like a lot considering the price of the visa but also they've saved me a lot of time so for me it's worth it.
You don't have to stay in the same country. I don't recommend you reapplying but if you apply in Malaysia and leave to Indonesia it won't matter. I've spoke to agents about this. I've also had friends personally apply in one country and then travel to other countries while it's being approved.
I'm pretty sure you need more than 6 months on your passport to enter Thailand regardless of what visa you have. The airline probably won't let you check in for your flight. It might go unnoticed with a land border but I would check with a visa run agency.