A brand refreshment will also be made to better define the 30-year-old complex, said Yongyuth Chaichana, managing director of Thippatana Arcade Co, operator of Pantip Plaza.
Pantip Plaza has large vacant spaces and has seen a sharp decline in sales after several shops or tenants closed their businesses because they were unable to deal with high rents.
Mr Yongyuth said the company will spend 300-500 million baht renovating Pantip Plaza in the busy Pratunam shopping area, with work starting in May and being completed early next year.
Pantip announced renovation plans two years ago but could not reach an agreement with tenants over how the work would affect their sales.
"We need to start our renovation now that Pantip Plaza is suffering with a 20% reduction in both sales volume and the number of visitors," said Mr Yongyuth, adding that 10 shops had already closed, resulting in an average 10% of vacant space.
He said the companies wanted to reduce the proportion of IT-related products sold at Pantip to 70% this year, down from 90%. The remaining 30% of space will be reserved for food areas, books, bicycles and lifestyle products.
Mr Yongyuth acknowledged that even though IT products play an important role in people's daily lives, the industry is on a downward trend.
IT products have now become a commodity, so there is less differentiation between products being sold, he said.
Consumers increasingly prefer to purchase technology products at their nearby residential areas or at IT shops in big department stores.
However, he said Pantip is located in a busy and convenient area with a variety of mass transport. The number of foreign customers accounts for 30% of visitors.
"We believe Pantip will become even more popular under the Asean Economic Community starting late next year," Mr Yongyuth said.
He said the company will need to raise its rental fees by 10% after it renovates Pantip.
Consumer spending is expected to recover in early 2015 if the country's political woes end, he said.
To boost sales during unfavourable economic conditions, Pantip will hold its annual Pantip Hot Sale with attractive offerings and heavy discounts at its three plazas from Saturday until April 6.