Macaques won the first round of their battle with park officials trying to trap them in Lop Buri province, where the catch was far below projections.
The Natural Resources, Wildlife and Plant Conservation Department had hoped to cage 30 monkeys on the first day of the operation on Monday, but later admitted only nine had been caught.
The Khao Sompoj no-hunting area is responsible for going after the macaques, but an official from there told Channel 3 the monkeys were already aware they were being hunted, and the vehicles and tactics used to catch them. The hunters would make some changes, including swapping their camouflage uniforms for civilian attire.
"Macaques are social animals. The ones in the cages have sent signals to the others, informing them how they were caught," said the official, whose name was not disclosed.
The three-day operation to thin the numbers of the frequently aggressive monkeys in Lop Buri municipality continues on Wednesday.
The same official said the operation on Tuesday had moved to other locations in the municipality. They were also being more selective, targeting aggressive monkeys and their leaders. Local residents were helping by pointing out the most annoying animals to the catchers.
The Natural Resources and Environment Ministry decided to take action to reduce the population after macaques injured people in three incidents this month.
Officials estimate there are about 2,700 monkeys roaming the municipality, most of them at Phra Prang Sam Yot historical site near the railway station.
The caught animals will be sent to a temporary shelter at the Wildlife Rescue Centre in Nakhon Nayok province while the park looks for suitable, permanent places to release them in Lop Buri province.
The rescue centre is in tambon Khao Phra in Muang district of Nakhon Nayok. It already houses at least 1,000 monkeys. The prospect of even more monkeys being kept there has alarmed people in the area, and they strongly opposed the move, according to One News.
Pongsawad Theerawattanakul, the president of the tambon Khao Phra Administration Organisation, said macaques escaping from the centre had already caused trouble for the community, scaring children and even damaging the local school.
"Local leaders agreed they do not want to see monkeys from Lop Buri in the area," One News quoted him as saying.
Wildlife rescue centre director Taweep Lomwong said the place could take no more than 50 macaques from Lop Buri, and they had already prepared cages for them.