SINGAPORE, Aug 23 (Reuters) - Singapore's manufacturing output probably rose in July as higher output of drugs provided a shot in the arm to a manufacturing industry burdened by weakness in the key electronics sector, a Reuters poll showed on Thursday.

The median forecast of five economists was for output in July to have climbed a seasonally adjusted 8.6 percent from June, when a slump in drugs production led to an unexpected 9.4 percent decline -- the sharpest fall in nearly six years.

Pharmaceuticals output is volatile because companies often switch products and shut down factories for certain periods to prepare for production of another drug.

Forecasts for manufacturing output ranged as widely as usual, from a rise of 2 percent to a rise of 10.5 percent.

Economists said the technology industry, which is facing a slowdown due to high inventories, may remain lacklustre for the rest of the year. The sector accounts for about a third of Singapore's factory output.

"The semi book-to-bill ratio dipped to 0.84 in July, from 1.00 in January, and that has certainly put the possibility of a tech recovery by the end of the year in doubt," said Irvin Seah, an economist at DBS Bank.

"On the other hand, pharmaceutical exports increased by 45.3 percent and this is likely to be reflected in the industrial production numbers as well. The transport engineering industry is also expected to add some much needed impetus to the industrial production growth."

The book-to-bill ratio compares the volume of orders for equipment to make chips to products shipped. In July, $84 of orders were received for every $100 of product billed.

Singapore's trade agency cut its 2007 growth forecast for non-oil domestic exports last month to 4-6 percent from 7-9 percent because of weak electronics shipments.

Singapore's manufacturing sector accounts for about a quarter of the city-state's $138 billion economy.

From a year earlier, manufacturing output was expected to have risen 3.7 percent in July, according to the median forecast of 10 economists, following a 7.4 percent drop in June.

Singapore makes about 30 percent of the world's hard-disk drives, but some of the big manufacturers are shifting production to cheaper locations.

Seagate Technology , the world's largest computer hard-disk drive maker, has moved production of its lower-end disk drives out of Singapore to China.

Singapore's Economic Development Board is due to release the manufacturing data on Friday at 1 pm SGT.

Forecasts for Singapore's manufacturing index in July:

Percentage change

------------------------

                                            vs July 06    vs June 07..

Action Economics                       5.5              9.8

ATR                                          3.0

CIMB                                         5.0              8.6

Citigroup                                     3.3              7.4

DBS Group                                  4.1

Forecast Ltd.                               5.3

HSBC                                         1.0

IFR THOMSON FINANCIAL            6.0             10.5

United Overseas Bank                 -2.2             2.0

UOB KAY HIAN                           2.8

------------------------------------------------

Median                                        3.7               8.6

High                                            6.0             10.5

Low                                            -2.2              2.0

.. Seasonally adjusted

.875 Not available