The SET Index rose by 10.8% during the first nine months this year, exceeding the average for the region and other emerging markets, spurred by an increase in vaccinations and a decrease in the daily infection rate.
Industries that outperformed the SET Index compared with the end of 2020 were industrial products, technology, agriculture and food, and service sectors.
According to Stock Exchange of Thailand senior vice-president Soraphol Tulayasathien, investors should monitor the direction of the Federal Reserve's tapering of its asset purchases, the downgrade of Chinese economic growth forecasts for 2021, and Beijing's tighter control over the country's property and technology sector.
He said an additional external factor is the US inflation rate, which started to rise because of an increase in energy prices.
Mr Soraphol said the recent inflation hike differs from the one in March because this time it was caused by the supply side.
This means it is possible the US government will raise interest rates sooner than expected, causing volatility in the global stock, bond, and money markets because the world uses US interest rates as a reference benchmark.
"If the interest rate rises quickly, it will affect growth stocks such as technology more than value stocks because growth stocks are mostly rising companies with a huge amount of loans, making their operational costs higher," he said.
Mr Soraphol said Thailand may see growth in exports as the baht weakens.
Tourism, which used to be a major source of income, should remain in a slump, he said.
The combination of these two factors means baht depreciation will not generate as much GDP growth as in the past, said Mr Soraphol.
Pakorn Peetathawatchai, SET president, said the stock exchange is preparing to launch an SME board later this year, which is a trading platform for small and medium-sized enterprises (SMEs) and startups to help them access capital markets.
Entrepreneurs and investors can look up information regarding the platform at www.live-platforms.com/education, he said.
Mr Soraphol said the SET and the Market for Alternative Investment's average daily trading value in September amounted to 101 billion baht, up 111% from a year earlier, while the daily trading value for the first nine months averaged 96.5 billion per day.
According to the SET, foreign investors were net buyers for a second consecutive month in September, tallying 10.8 billion baht.
However, they remained net sellers of 79.2 billion baht during the first nine months.
The SET also recorded the highest value of initial public offerings in the region at US$3.33 billion for the first nine months.
The trading volume of derivatives averaged 679,223 contracts per day in September, up 43.6% from the preceding month.
During the first nine months, the average daily trading volume stood at 550,194 contracts, an increase of 8% from the same period last year, mainly driven by more trade in single stock futures, gold online futures and USD futures.