Thai Oil Q2 profit down 41 pct, shares fall

* Net profit down 41 pct, near forecasts

* Q2 sales down 44 pct as prices of oil products fall

* GRM down to $1.2 a barrel vs $9.6 a year earlier

* Shares underperform; H2 earnings seen weak

BANGKOK, Aug 11 (Reuters) - Thai Oil PCL TOP.BK (TOP), the country's top oil refiner, reported a 42 percent fall in its second-quarter earnings on Tuesday after its gross refining margin dropped, reflecting weakness in the economy.

Despite strong growth from the previous quarter, earnings were expected to be weak in the second half as new capacity could put pressure on product prices, analysts said.

After the earnings announcement, Thai Oil shares were down 1.9 percent at 39.25 baht at 0411 GMT, while the main Thai index was 0.5 percent lower.

Thai Oil, nearly half-owned by energy company PTT PCL PTT.BK, reported a net profit of 6.2 billion baht ($182 million), or 3.03 baht per share, down from 10.55 billion baht a year earlier.

Eight analysts surveyed by Reuters had on average forecast a net profit of 6 billion baht for the April-June quarter.

But earnings were almost three times higher than the 2.28 billion baht made in the previous quarter thanks to an improvement in its petrochemical business and huge inventory gains as oil prices recovered.

Second-quarter sales dropped 44 percent from a year earlier to 70.6 billion baht, while its gross refining margin was at $1.2 a barrel, down from $9.6 a year earlier due to weak demand, it said in a statement.

Its integrated margin, which includes its petrochemical business and the impact from oil inventories, was $10.8 a barrel in the second quarter, down from $26.3 a year earlier.

Its refinery ran at 98 percent in the April-June quarter, down 7 percentage points from 105 percent a year earlier because it shut down a hydrosulfurization unit for two weeks in May, it said.

In the past three months, the stock has risen 15 percent, underperforming a 22 percent increase in the overall stock market .SETI. ($1= 34.01 Baht) (Reporting by Khettiya Jittapong; Editing by Alan Raybould)