I think you can carry as much as you want but you need to declare it at customs when it reaches a certain amount. I carried $9,900 USD into Thailand once and avoided the need to declare $10,000.
If you are asking about using the monthly income method to meet the 1 year extension financial requirements then you need to deposit at least 65,000 baht to your bank account each month. You have to show that the money came from outside Thailand (an international transfer).
If you are using the 800,000 baht deposit method then the whole 800,000 must be on deposit in your Thai bank account.
Why anyone would consider depositing exactly 800,000 baht to meet immigration requirements without having a substantial buffer on top of it to account for currency exchange rate fluctuations and mysterious unexpected banks fees is beyond my thinking.
If your US Social Security income is less than $25,000/year there is no tax. After that you would pay tax on 85% of SS. Exactly how much depends on your particular tax return. If you are talking about Social Security or the equivalent outside the United States then I don’t know.
I checked earlier and the exclusion was $120,000 in 2023. Getting another passport is the first step and unless you have a familial relationship with another country it could require expensive investments in that country to get a passport. Getting a Thai passport has its own difficulties.
All the information on this that I find is similar to this
How much does it cost to renounce US citizenship in 2023?
To renounce your citizenship, you must have been tax compliant for five years and subsequently pay any outstanding tax bills that you may owe.
Additionally, you must prove by the following June 15th that you’re compliant for the five years before renunciation. So, on the date of the appointment, you may be behind, but you have until the following June 15th to meet the threshold to be deemed in compliance. If you’d like to simulate the renunciation process, connect with a US expat tax expert.
Those hoping to renounce their US citizenship must also pay a non-refundable renunciation fee of $2,350 for administrative processing.2
Certain expats, classified as “covered expatriates,” are also subject to an additional expatriation tax, or exit tax. Generally, a covered expatriate is somebody who either:
Has had an average income tax of more than $178,000 over the past five years before their renunciation date,4 OR
Owns more than $2 million in worldwide assets, OR
Fails to certify that they have been compliant with their tax returns over the past five years.
Most often, covered expatriates subject to the exit tax are taxed on the fair market value of their assets at a long-term capital gains rate of 23.8% (excluding the first $767,000).5 The exit tax, in other words, is imposed as if you’d sold all of your worldwide assets on the last day that you held US citizenship. There are exceptions to this rule, but it can be difficult to predict which assets will classify as such, and how they will be taxed.