Visa Help For Less 50yrs Old

I've got a combination question, some parts of which have surely been answered before but I'd appreciate your feedback on the whole picture. Here goes.

Some background information:

My girlfriend and I have been together for a few years.

She is due to have our first baby in July.

I want to register it as our baby with the relevant UK and Thai authorities as soon as practical.

I am 38, live here in Thailand but do not work. I have no real intention to return to "work" outside of SE Asia and in all liklihood will just develop, buy and sell businesses if I do anything at all.

I have a business visa which expires end 1st quarter 2008 but do not want the hassle of flying back to the UK each year to get it renewed. I do not like having to keep going out of the country each 90 days.

We have, in my girlfriend's name, just bought a new truck on finance over 4 years. She does not technically have a job or pay taxes on such.

I would like her to obtain a mortgage in perhaps a year on the basis of income earned.

OK, so now my questions.

As the end goal is to get her a mortgage, I understand that unless she shows accounts from her business for at least 2 years, she would have to have a job where she earned the requisite income. Checks would be far greater than for a car loan so can I assume that together with a letter from her employer and potential salary slips, they would want some official forms from the tax office ? If so, how often are these forms given to the taxpayer ? If only once a year for example, then someone working for 9 months would not necessarily have one. Would they then be unable to get a mortgage ?

I understand that a husband, not just the father of a child, is eligible to obtain a visa to remain in Thailand if the family has a tax paid income of Bt40,000 per month. Is this figure of Bt40,000 before tax or afterwards ? How long would the wife have to earn this sum and pay tax on it before the husband could make a successful visa application based on her and thus the family's income ?

From my early research, the easiest way to accomplish all things is to get married, have her work in a job where she earns over 40k and pays tax. This should allow me to get a visa and her to get a mortgage after time.

Any help more than useful. Thanks.