Thailand's industry-wide auto sales might slump up to 15 percent this year and deliver a third consecutive year of negative growth, according to the Thai subsidiary of Japan's Toyota Motor Corp. The company had initial expectations that called for a positive turn of events - with new vehicle sales soaring 4.3 percent this year to a total of about 920,000 units - but was forced to modify its estimate in July to just 800,000 autos and now on Monday it further cut the range from 750,000 to 760,000 vehicles. "The domestic economy has been for us for a while.