(Updated at 0910 GMT)

* S&P to wait until August to make key Kenya rating call

* Hungary central banker says July rate cut an "open question"

* Thailand approves $2.8 bln soft loan scheme for commercial banks

* S.Africa to cut interest rates in September, Poll shows

* Stocks off 0.2%, FX flat

July 16 (Reuters) - Most emerging markets stocks and currencies were flat to slightly lower on Tuesday, as investors awaited details on reforms out of China and assessed the implications of a second Donald Trump presidency in the U.S.

MSCI's index tracking bourses in developing economies slipped 0.2%.

China's Shanghai stock index closed flat, while Hong Kong stocks notched its second-straight day in losses. Caution loomed with the 'Third Plenum' under way, at the end of which markets expect the Communist Party to outline reforms to support the local embattled economy.

Investors were also focused on the fallout on inflation and trade in developing economies if former President Donald Trump wins a second term.

"It would be perfectly reasonable to argue that Trump 2.0 would be negative for export oriented EM economies, in particular those that rely strongly on China," Piotr Matys, senior FX analyst at In Touch Capital Markets.

Matys said Trump's fiscal policies are seen as inflationary, which would limit scope for manoeuvre for the Federal Reserve.

An index tracking currencies was not trading far from the flat mark. The index has been trading tepidly over the past six weeks as uncertainty looms on the timing of the interest-rate cut.

In central and eastern Europe, Hungary's forint was flat relative to the euro. A possible further small reduction in Hungary's base rate is an "open question" for the central bank at its policy meeting next week, Deputy Governor Barnabas Virag said.

South Africa's rand edged up 0.2%, from a 1.4% drop in the previous session. A Reuters poll showed the domestic central bank might cut rates by 25 basis points in September as inflation cools.

Kenya's shilling weakened 0.3% against the euro, while yield on 5-year sovereign bonds climbed 15 basis points (bps).

Ratings agency S&P Global said it plans to wait until a scheduled review date on Aug. 23 to decide whether to cut the east-African nation's sovereign credit rating.

Against the backdrop of a slow economic recovery, Thailand's cabinet approved a $2.8 billion soft loan scheme where commercial banks could lend to borrowers at below-market rates. The baht was flat against the dollar, while local equities lost 0.5%.

A stress test of banking systems in Zambia, Ghana, Rwanda, Morocco and Mauritius found some lenders in the region could face collapse if nature loss slashes the profits of agriculture and forestry firms they have lent to.

Rwanada's franc was muted against the euro, as early results from presidential elections put incumbent Paul Kagame in the lead, while Syria's pound was flat, with parliamentary elections expected to yield few surprises.

(Reporting by Johann M Cherian in Bengaluru; Editing by Arun Koyyur)