Earlier, the average had been down more than 88 points.
The yen and gold continued rising, while the Swiss franc took a breather against the dollar (last trading at 0.9660 francs) and the euro, but kept most of its yesterday's hefty gains. Major indexes in Asia closed lower.
The decline followed overnight losses on Wall Street.
The Thai stock market has alternated between positive and negative finishes through the last five trading days since the end of the two-day winning streak in which it had gained nearly 5 points or 0.3 percent.
"Right now the market is viewing it as a lot of saber-rattling and a lot of smoke, but not much fire", said Darrell Cronk, president of Wells Fargo Investment Institute. Tensions spiked yet further when North Korean state media later said Pyongyang was considering strikes near U.S. military installations in Guam.
The Japanese yen hit an eight-week high against the USA dollar, while spot gold also reached a two-month high. But the moves were modest.
In other energy futures trading, wholesale gasoline dipped one cent to 1.62 dollars a gallon.
The Swiss franc and Japanese yen are often sought in times of geopolitical tension or global financial stress, partly because both countries have big current account surpluses.
Watch maker Fossil Group plunged 25 percent after reporting a weak quarter.
Shares of Walt Disney were down 4.23 percent, the biggest drag on Dow, as investors doubted whether the company can succeed with its plan to launch its own streaming services rather than rely on Netflix to reach online viewers.
Gold fell 2.10 to 1,262.60 dollars an ounce.
The S&P 500 has hadn't a single day move of more than 0.5 percent since mid-July and has fallen more than 1 percent only twice this year. On Comex, the gold price climbed 0.9% to $1,274.30 an ounce, while silver rose 1.4% to $16.61 and platinum added 0.4% to $976.15. The FTSE All World index was down 0.3% in London's morning trade.