DUBAI, March 19 (Reuters) - Stock markets in the Gulf edged down in thin early trade on Sunday as some investors cashed out of blue chips.

Dubai's index lost 0.6 percent with a 1.9 percent drop by heavyweight Emaar Properties. Shuaa Capital rose 0.5 percent but GFH Financial fell 0.4 percent. Last week the firms announced they were in preliminary talks on a possible merger.

In Qatar, 20 companies will see a doubling of their investible weight factors on Monday in the second phase of Qatar's upgrade by FTSE Russell to secondary emerging market status.

But only seven of those companies rose early on Sunday; commodities shipper Qatar Navigation was the top performer among them, adding 2.1 percent.

The stock index was down 0.2 percent as most banking shares fell, with Qatar National Bank down 0.6 percent.

Saudi Arabia's index slipped 0.1 percent in the first 40 minutes of trade as most petrochemical shares fell. Bellwether Saudi Basic Industries lost 0.5 percent.

Mid-sized Astra Industrial Group, however, rose 1.3 percent after its board recommended a dividend for 2016 of 0.5 riyal per share, lower than the cash payout of 0.75 riyal a year earlier but higher than some had expected.

Kuwait's index, which has been outperforming its peers since the start of the year, added 0.4 percent. Telecommunications operator Zain jumped 3.5 percent.

(Reporting by Celine Aswad; editing by Andrew Torchia and Jason Neely) ((celine.aswad@thomsonreuters.com)(+9715 62247653)(Reuters Messaging: celine.aswad.thomsonreuters.com@reuters.net))