If you assume CLmax remains constant then stall EAS remains constant. In IAS terms this means stall speed increases slightly as you climb, from the compressibility corection. However, CLmax does not remain constant. At quite low mach it begins to degrade, so stall speed rises, even in EAS. The low speed buffet boundary curves toward the high speed boundary, usually Mmo. Where they meet is coffin corner. Buffet boundaries are given at a percentage above the stall speed and turbulence boundaries equate to load factor increases, so are tighter.
Dick w