it doesn't matter who is saying anything to get their name out there, until it is published in the Royal Gazette it means nothing. If you follow the Thai government you'll see this happening all the time. High ranking people just saying things to get their name in print.
that two entries was only for land border crossings, and it ended July 15th of this year. There are no limits as long as you are following a pattern of being a tourist, which your plan does.
until it is published in the royal gazette what rumors you hear mean nothing. The tax laws have always been 180 days in Thailand making you liable for Thai income tax. That is nothing new.
do not bother buying a tourist visa before you enter the country. It is a waste of money. You get a 60 day visa exempt entry each time you enter the country. Your plan follows a normal pattern of being a tourist, as lots of people base out of Thailand when visiting other countries. You are not crossing the border and immediately returning, and, you are not getting the 30 day extensions you could get. You are following a normal tourist pattern, and as long as you have a ticket booked for your next excursion into the next country, not the same one each time, immigration won't care. Your plan is good, except buying a single entry tourist visa. That is a waste of money.