Assuming you have 3 kids they can each sponsor one adult on a Guardian non O immigrant visa. So you wouldn't require a DTV. You won't be able to work but you can reside in Thailand so the financial proof is important to show you can support the family during your stay. Check the Canadian e-visa website for all requirements including the financial proof. The list is short and concise.
Step 1 is applying for your kids ED visa which you do online and with supporting documentation from their school.
Once kids obtain ED visa you can then apply for Guardian visas.
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