* To increase investment by more than 62 pct this year
* Internet revenue jumps 76 pct
* CFO to retire
* Share price up 75 pct this year (Adds quotes, details)
By Helen Nyambura-Mwaura
JOHANNESBURG, Nov 26 (Reuters) - South African e-commerce and media group Naspers sees lower full-year earnings after it plans to increase investment into Internet platforms and digital pay-TV by more than 62 percent to lock in more customers.
Johannesburg's biggest local company by market valuation posted a 16 percent rise in core headline earnings in the first six months to end September, but will spend more than 7 billion rand ($695 million) to market e-commerce platforms and roll out digital terrestrial television across African cities.
After starting life as an Afrikaans-language newspaper, Naspers has grown quickly to showing English Premier League matches across soccer-mad Africa and owning stakes in online retailers and gaming companies in Russia and India.
"It's a very competitive market, the consumer always goes for the best product. Your only chance is to have the best product in the market," said Chief Executive Koos Bekker.
Naspers second-half spending is traditionally higher from subsidising decoder purchases that are typically done over the holiday season, and advertising its online e-commerce to target Christmas shoppers.
In Kenya, Naspers expects to sell "hundreds of thousands" of decoders in December as the country adopts digital television transmission, Bekker told Reuters.
Its main growth market is no longer South Africa anymore, but Kenya, Nigeria and Ghana, he said.
"What you are seeing here is a company that is growing very, very fast, they are investing for more growth and you will always have a question on that," said Reuben Beelders, portfolio manager at Gryphon Asset Management.
"What is evident is that they have produced an excellent result, but they are being cautious about the next six months."
The sprawling media group with holdings in emerging markets e-commerce companies such as Chinese giant Tencent Holdings said revenue from Internet platforms expanded by 76 percent to 24.9 billion rand ($2.5 billion).
Core headline earnings came in at 1,248 cents per share.
Naspers said Steve Pacak would retire as chief financial officer June 30, and would be succeeded by Basil Sgourdos, CFO at subsidiary MIH Holdings.
Naspers' share price had dropped nearly 2.5 percent to 948 rand at 0934 GMT. The stock has rallied more than 75 percent this year, taking its market value to more than $40 billion.
The stock is trading at a price-to-earnings ratio of 63 times, the second most expensive share among Johannesburg's Top-40 companies after Impala Platinum. ($1 = 10.0769 South African rand) (Reporting by Helen Nyambura-Mwaura; Editing by Tiisetso Motsoeneng and Elizabeth Piper)