Total sales rose 5.85% on year to 2.83 trillion baht in the first quarter despite unfavourable economic and political circumstances, according to the Stock Exchange of Thailand.
Of all 511 listed companies, 471, or 92.17% have reported their first-quarter earnings, SET senior vice-president Paveena Sriphothong said in a statement released on Tuesday.
Among them, 384 companies (81.53%) reported a net profit.
Their combined gross profit margin was 18.29%, a slight decline from 18.37% recorded in the same period of 2013, while their net profit margin also dropped to 7.79% from 9.15%.
Their debt/equity ratio, excluding those from the financial industry, was 1.31 times.
"SET-listed companies could still maintain their sales and abilities to record good gross profits, compared with the same period last year when the country's economic and political environments remained more favourable," she said.
However, the decreased margin from exchange rates, as well as increased selling, general and administrative expenses and interest rate burden, put pressure on the net profits of large and medium-sized SET100 listed companies, which were down 18.49%.
Net profits of non-SET100 listed companies rose 54.73%, mainly due to the increase in net assets from the TRUEIF's performance worth 15.77 billion baht.
Excluding the amount, the non-SET100 listed companies' net profits saw a slight decline of 0.35%, said Ms Paveena.
"Moreover, Thailand's economic slowdown and prolonged political turmoil have continued to pressure down sales of listed firms.
"Hard-hit businesses included those from retail, media and publishing, airlines, and securities industries," she said.
"Meanwhile, businesses from electronics and food sectors looked set to enjoy a continued growth in their sales due to favourable prices and volume from both within and outside the country, as well as the weak baht," Ms Paveena added.
The top five firms with the largest profits were PTT, Siam Commercial Bank (SCB), PTT Exploration and Production (PTTEP), Kasikornbank (KBANK) and Advanced Info Service (ADVANC).
The top three industry groups with highest profits were financials, resources and technology.
Of the total of 28, the top three sectors with the largest profits were energy & utilities, banking and information & communications technology, with a combined net profit of 145.30 billion baht or 65.96% of total net profit.
Their combined sales accounted for 53.70% of total sales.