What are the best options for extending my stay in Thailand on a tourist visa while consulting for a company?

Oh boy... here we go:

" Is it true about the new regulation providing you a six month tourist visa and unlimited land-boarder crossings? Would it be possible to spend a year just by renewing my tourist visa?"

Not true. If there are any changes, I expect it to get tighter, not looser. You'd have to find some type of valid visa to stay here. Good options to look into are:

1. Non-B visa based on either the company who's you're working for, or through a company like Iglu.

2. (Illegal, expensive, but possible) the Thailand Elite Visa. Legally, you can't work on it.

You should be paying income tax and be part of the social security scheme.

"Is it hard to get a Non-Immigrant Visa “B” and in which embassy would it be easier to make it? Could my already two entries create problems for the business visa? "

It's up to the company to get the paperwork to do the Non-B. As an employee, your job is to deliver the paperwork to the consulate. The last I heard, Vientiane, Laos is the best consulate to get the Non-B.

" Could my already two entries create problems for the business visa? "

No.

You need a Work Permit, the company can apply at the Ministry of Labor and next to this you need to get the Non Immigrant B visa, which you can get at a local Immigration Office if the company can and is willing to meet the requirements or after application of the work permit you can apply at a Thai Consulate.

Technically, you need a work permit to do consulting AFAIK. You need a work permit for any revenue generating activity in Thailand. And even for voluntary work.