When you have this fly into Thailand and open a bank account in your own name and deposit 400,000 baht into it. Wait 2 months then apply for a spouse visa.
Don't use an agent as it is expensive and you can get through the visa process without an agent, just provide the information and documents requested by immigration.
The difficult part is opening a bank account, but shop around. I used Bangkok Bank, but had to try several branches to find one that would open it. Go smartly dressed, be polite and take your wife and her house details.
maybe simply ask DLT. That way you can be certain.
Like you, I would always be cautious about this type of advice, indeed my licence needs extending next year, but I intend to do it at the end of the 2 years to be certain.