DSME signed a contract with Indonesia on for the supply of three Improved Chang Bogo class submarines. These submarines will be equipped with Atlas Electronic CSU 90 hull-mounted passive and active search-and-attack sonar and flank sonar arrays, Indra's Pegaso RESM system and Aries low-probability of intercept radar, L-3's MAPPS integrated platform management systems[38] and Sagem's Sigma 40XP inertial navigation systems.
The South Korean Chang Bogo-class submarines, originally based on Type 209/1200, had reportedly been heavily upgraded from a time early in the 21st century,[5] which if properly undertaken was supposed to include domestic hull stretch augmentation from 1,200 tons to 1,400 tons, and installment of domestically developed Torpedo Acoustic Counter Measures (TACM).[6][7] These upgrades could have been affected due to Korean economic problems of the late 1990s, which affected other plans to acquire nine 1,500-ton AIP-equipped boats or upgrade six 1200 boats to 1,500-tons AIP-equipped boats,[6][8][9] although the more ambitious plan to acquire nine 1,800-ton Type 214 AIP submarines was preserved and put under progress, which will reportedly be wrapped up in 2018 when all submarines of the type are scheduled to be commissioned. Outfitting the submarines with Sub-Harpoon launching capability was a part of the upgrade,[6] and this seems to have been properly carried out by 2002 on at least one submarine. By 2007, Na Daeyong and Lee Eokgi were demonstrated to have the capability.[1][10] In the 2008 RIMPAC the submarine Lee Sunshin also demonstrated its sub-harpoon capability.[11] By 2009 it was reported that nine South Korean-modified 1,400-ton Type 209 submarines were in service with the ROKN.[12][13] As of 2011 they were reported to be 1,200-ton Type 209 submarines.[14][15] They can equip the White Shark heavy torpedo,[7][16][17] and can possibly equip submarine-launched Hae Sung anti-ship missiles later on.[18][19] LIG Nex1 began producing TACM for unspecified submarine types of the ROKN as well, which finished development in 2000.[20][21] AIP and flank-array sonars are planned for future modernizations.[15] The Chang Bogo class offered to Indonesia will already be in stretched and augmented forms including guided missile-launching capabilities and a surface displacement of 1400 tons, quite similar to the original plan to upgrade the existing Chang Bogo class submarines of ROKN to similar specifications.[2]

A science documentary by EBS has revealed that Chang Bogo-class submarines undergo major generational overhaul and refit every eight to twelve years.[22] The overhaul and refit involves periodic cutting, complete disassembly, and rewelding of the hull for the upgrade or total replacement of the submarine's old engines, navigational equipment, batteries, and other essential equipment with their modern counterparts.[22] Hull stretch may also have taken place in some of the Chang Bogo-class vessels since the early 2000s, but it has neither been completely confirmed nor denied. Some Chang Bogo-class vessels are demonstrated to have sub-Harpoon launching capability when previously the class was lacking it. ROKN is committed to build and maintain a submarine force of 26 attack submarines until 2025, excluding small and midget submarines, though it is not clear how many submarines among those will belong to the Chang Bogo class.[23] The oldest commissioned Chang Bogo class submarine by then will be 32 years old.

Lithium-ion battery power stacks are being developed to increase the underwater endurance of Chang Bogo-class submarines by two to three times, offering four to five times the power density of Type 209's current lead-acid batteries and as much as twice the power density of Type 214's BZM 120 fuel cells.[24][25]