1. Chose launch modding tool when you start the game.
2. Just press "X" on the starting prompt
3. Press the "Open any" button on the right of the tool bar
4. Open the quicksave.save at C:\Users\*your username*\AppData\Local\kenshi\save of the save you need to edit
5. Select "Southern Hive"
6. Find the one with the value "204-gamedata.base" and you will know the ID for your faction. For example if you have a relationSID19 | 204-gamedata.base, then the number you need to change will be "relation19"
Enter whatever number and save and profit!

Requirement: Skeleton PC, ♥♥♥♥ ton of cash, too much time to spent, a lot of victims.

1. Go to Flat Lagoon, find a southern hive pacifier in the bar.
2. Pay him the number he ask for, as it is too long ago I forgot the exact number but it should be under 100,000 cat. This put you relation to -10 and you are no longer attack on sight. (For your skeleton at least, your meaty companion are still food.)
3. Find some meatbag victims, you can go hunt for bandit, recruit from bar, kidnap from city. Your choice.
4. USE YOUR SKELETON, AND DON'T BRING YOUR MEATBAG FRIEND.
5. While carry a meatbag victim, talk to anyone walking OUTSIDE a house. select the option about giving the victim to king as a tribute. you get 1 relation point per victim. (Going inside a house without being ally will get you attacked, select the option about teasing will also get you attacked.)
6. Repeat until you get to 50 relation. There, you earned some new friend. (It stop here, I can't tribute more after 50 relation. Can't talk about it)

It is worth it? NO.
All those work and all you get is access to 2 bar and 1 weapon store. maybe a place to rest before sonorous dark but you can get about the same effect just by talking to Elder in Iron HQ.
Well you can't buy food in Iron HQ but you have plenty of chance to stock up anywhere. Maybe Mourn, maybe Flat Lagoon, maybe Brink, maybe Black scratch, maybe Crab village, maybe make an outpost and do it yourself.
The best utility I can thought of is to ally both Southern Hive and Skin Bandit. Then you can just simply walk into Ashland.
But you can just build a bridge at sniper tower after you ally with both Crab raider and Skeleton bandit and achieve the same effect.
Decision...
Decision...

Extra
I had tried to kidnap the southern hive queen and put her into a peeler and see if I can ally southern hive by healing her. But the result I get top at 5. Can worth 55 meatbags. Risk turning the whole place to Fogmen.