Question: How do YOU pronounce the letter combination "th" in english?

I'm currently writing a fantasy novel set in the past. It's inspired by Victorian-era London, but the story is set in a fictional world where there are a few more species with their own cultures and histories. It's an adult novel, and it's a pretty dark story. It's inspired by the works of Anne Rice and Poppy Z. Brite. <br><br>One of the main characters is a creature with qualities similar to a vampire. The lore is that they came from a place where "th" was pronounced as "t" and "h" which is the norm. It's like how the "th" in "this" and "that" are pronounced as a "d" sound. This character is not the protagonist, he's not a villain but also not a hero in this story. He's an anti-hero. I want to show his unusual speech pattern in the dialogue without being confusing and hard to read. I'm planning on spelling words with "th" like: "this" as "tis" and "that" as "tat". However, I'm planning on spelling words like "thought" and "thousand" as "tot" and "tousand". <br><br>Will that be confusing or hard to read?