The Director of the Department of National Parks, Wildlife and Plant Conservation, Manopat Haueungkaew, said the earlier opening would help to generate more revenue.
Officials closely involved with the Similans - regarded as the best diving and snorkelling that the Phuket Andaman region has to offer - are downplaying environmental concerns.
It has even been alleged that hundreds more trippers to the park are being permitted entry with tour operators and rangers pocketing the extra cash.
Today the Director of the Similan Islands park, Nat Kongkesom, said the new opening date of october 15 was to abide by government policy to expand income from tourism.
He said that ''good weather'' usually ensued at that time of the year, although traditionally the monsoons have kept the Similans closed until November 1.
Reefs that continued to recover from coral bleaching would remain closed, he said.
When asked how many visitors the Similans could sustain each day, Khun Nat said he was at Phuket airport awaiting a flight to bangkok and did not have his handbook with him.
People who visit the Similans in November usually find the region has fully recovered after a six-month break from tourism while those who travel there in April find the beaches and the reefs in different condition.
Tourism officials on Phuket and elsewhere complain that the increase in arrivals from China and Russia has meant larger numbers of smokers who dump butts in places of natural beauty and sometimes souvenir pieces of coral.
At least one Phuket official believes that most Chinese who come to the region are usually only here for three or four days and are less caring ''visitors'' rather than tourists.
The Similans, consisting of nine islands and home to a turtle sanctuary protected by the Royal Thai Navy, are usually reached by speedboat from Tablamu Pier in Phang Nga, the province north of Phuket.