You can open a company with a thai partner and be a share holder/ board member. But being under dtv means you can not legally pay yourself a salary. It might be a better option to consider applying for a wp/non-b visa based on the company.
For PR you need to be a tax resident for 3 years, im not too sure if the type of visa matters as much as your contribution to nations coffers in terms of tax, usually taxable income that qualifies does have a lower bound, i dont remember the exact amount, taxable income of 85k a month I think.
In short whether you spring for dtv or ltr make sure you meet the tax contribution requirements either as an investor or business owner.