* SoftBank expected to finalise Grab investment this month
* Grab plans to use part of new funds to expand in Indonesia
* SoftBank first bought stake worth $250 million in Grab in 2014 (Adds Grab's investment and expansion plans; context)
By Anshuman Daga
SINGAPORE, Dec 21 (Reuters) - SoftBank Group Corp is nearing a deal to invest $1.5 billion in Grab, three times a previously expected $500 million, as Southeast Asia's biggest ride-hailing firm looks to expand, a person with knowledge of the matter said.
Six-year old Grab has so far raised over $6.5 billion, led by SoftBank, Chinese ride-hailing firm Didi Chuxing and Toyota Motor Corp. After a fund raising in August, Grab was valued at around $11 billion.
SoftBank first bought a stake worth $250 million in Grab in 2014 just as Grab began competing with Uber Technologies in Southeast Asia.
Its latest funding in the ride-hailing firm will be made from its Vision Fund, which after raising more than $93 billion last year is the world's largest private-equity fund.
SoftBank is expected to finalise its investment in Grab this month and an announcement is likely next month, said the person, declining to be identified as the information is not public.
Grab declined to comment, while a SoftBank spokesman did not have an immediate comment.
Reuters reported in October that SoftBank was closing in on a deal to invest about $500 million in Grab, underscoring the tech investment giant's confidence in the ride-hailing firm's growth.
Grab acquired Uber's Southeast Asian business this year in exchange for a stake in itself and has since expanded its operations rapidly.
Grab is looking to use part of the funds to expand further in Indonesia, where it has partnerships with fintech firm OVO and e-commerce platform Tokopedia, the person said.
The firm is looking to transform itself into a leading consumer technology group offering, besides ride-hailing, services such as food delivery, electronic money transfers and mobile payments in one of the world's fastest-growing markets.
Grab and its Indonesian rival Go-Jek are raising billions of dollars and investing in the race to corner a bigger share of Southeast Asia, as more of the region's 650 million consumers go online and use smartphones to shop, commute and make payments.
Go-Jek kicked off a trial launch of its ride-hailing service in parts of Singapore last month and plans to roll out an array of services through its app in early 2019, challenging dominant player Grab in the small city-state. (Reporting by Anshuman Daga in SINGAPORE, additional reporting by;Aradhana Aravindan in SINGAPORE and Taiga Uranaka in TOKYO; Editing by Himani Sarkar and Christopher Cushing)