Games like Thekku Island
Games like Thekku Island include Escape the Backrooms, Five Nights at Freddy's: Security Breach, SOMA, Firewatch, and Outer Wilds. We matched them by the tags players give Thekku Island on Steam (Exploration, 3D, Adventure, First-Person, and Horror): closest matches first, and among equally close ones the better-known games.

Escape the Backrooms
Shared: Horror · Psychological Horror · Exploration

Five Nights at Freddy's: Security Breach
Shared: Horror · First-Person · Exploration

SOMA
Shared: Horror · Psychological Horror · Exploration

Firewatch
Shared: Adventure · Exploration · First-Person

Outer Wilds
Shared: Exploration · Adventure · Story Rich

What Remains of Edith Finch
Shared: Exploration · Story Rich · First-Person

MiSide
Shared: Psychological Horror · Horror · First-Person

Poppy Playtime
Shared: Horror · First-Person · Singleplayer

Inside the Backrooms
Shared: Horror · Exploration · Psychological Horror

Lethal Company
Shared: First-Person · Horror · Exploration

SILENT HILL: Townfall
Shared: Adventure · Horror · Exploration

Outlast
Shared: First-Person · Horror · Psychological Horror

Amnesia: A Machine For Pigs
Shared: Horror · Exploration · First-Person

Resident Evil Requiem
Shared: Horror · First-Person · Survival Horror

Amnesia: Rebirth
Shared: First-Person · Exploration · Adventure

The Complex: Expedition
Shared: Exploration · Horror · Psychological Horror

Backrooms: Escape Together
Shared: Horror · Psychological Horror · First-Person

SILENT HILL 2
Shared: Horror · Psychological Horror · Story Rich

Layers of Fear (2016)
Shared: Horror · Psychological Horror · First-Person

Five Nights at Freddy's: Secret of the Mimic
Shared: Adventure · First-Person · Horror

Resident Evil 7 Biohazard
Shared: Horror · First-Person · Survival Horror

Subnautica 2
Shared: Exploration · Horror · First-Person

Visage
Shared: Horror · Psychological Horror · First-Person

Darkwood
Shared: Adventure · Horror · Psychological Horror