SET_PED_ONTO_MOUNT

void __fastcall set_ped_on_mount_func(__int64 ped, __int64 horse, signed int seat_place, char must_be_true)
{
  char smth_bool; // r12
  signed int seat; // esi
  __int64 horse_; // rbx
  __int64 ped__; // rdi
  signed __int64 get_ped_addr; // rax
  signed __int64 ped_addr; // r15
  int v10; // er9
  unsigned __int64 v11; // rax
  unsigned int v12; // er14
  signed __int64 v13; // rdx
  unsigned __int64 v14; // rsi
  unsigned __int64 v15; // rbp
  unsigned __int64 v16; // rax
  unsigned __int64 v17; // rcx
  char v18; // ST30_1
  signed int v19; // ST28_4
  __int64 v20; // ST20_8
  signed __int64 v21; // rcx
  unsigned __int64 v22; // rsi

  if ( ped )
  {
    smth_bool = must_be_true;
    seat = seat_place;
    horse_ = horse;
    ped__ = ped;
    get_ped_addr = sub_7FF6FF5C9448(ped);
    ped_addr = get_ped_addr;
    if ( horse_ )
    {
      if ( get_ped_addr )
      {
        v10 = dword_7FF70226C908;
        v11 = *(328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908) + qword_7FF70226C910 + 160) & 0xFFFFFFFFFFFFFFFEui64;
        if ( v11 & -(*(328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908) + qword_7FF70226C910 + 160) != 0i64) )
        {
          if ( *(*((v11 & -(*(328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908) + qword_7FF70226C910 + 160) != 0i64))
                 + 0x10)
               + 32i64) > 0.0 )
          {
            v12 = -1;
            if ( seat >= -1 )
              v12 = seat + 1;
            v13 = 328i64 * ((*(ped__ + 156) & 0x1FFFFu) - dword_7FF70226C908);
            v14 = *(v13 + qword_7FF70226C910 + 184) & 0xFFFFFFFFFFFFFFFEui64 & -(*(v13 + qword_7FF70226C910 + 184) != 0i64);
            v15 = *(v13 + qword_7FF70226C910 + 32) & 0xFFFFFFFFFFFFFFFEui64 & -(*(v13 + qword_7FF70226C910 + 32) != 0i64);
            if ( smth_bool )
            {
              if ( sub_7FF7014D20E4(horse_, 0i64) && !*(sub_7FF7014D20E4(horse_, 0i64) + 338) )
              {
                v16 = *(328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908) + qword_7FF70226C910 + 184) & 0xFFFFFFFFFFFFFFFEui64 & -(*(328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908) + qword_7FF70226C910 + 184) != 0i64);
                *(v16 + 16208) |= 0x40ui64;
                v13 = -*(328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908) + qword_7FF70226C910 + 32);
                v17 = *(328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908) + qword_7FF70226C910 + 32) & 0xFFFFFFFFFFFFFFFEui64 & -(*(328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908) + qword_7FF70226C910 + 32) != 0i64);
                *(v17 + 116) |= 0x10u;
              }
              *(v14 + 16208) |= 0x40ui64;
              *(v15 + 116) |= 0x10u;
            }
            LOBYTE(v10) = 1;
            v18 = 0;
            LOBYTE(v13) = 1;
            sub_7FF6FF1FB478(v14, v13, 1, v10, 1);
            v19 = 268435552;
            LOBYTE(v20) = 1;
            sub_7FF6FF368E5C(ped_addr, horse_, v12, 0i64, v20, v19, v18);
            v21 = 328i64 * ((*(horse_ + 156) & 0x1FFFFu) - dword_7FF70226C908);
            v22 = *(v21 + qword_7FF70226C910 + 208) & 0xFFFFFFFFFFFFFFFEui64 & -(*(v21 + qword_7FF70226C910 + 208) != 0i64);
            if ( v22 )
            {
              sub_7FF700BCFDB4(ped__, horse_, 0i64);
              sub_7FF70045C428(v22 + 1728);
              sub_7FF70045C420(v22 + 1728);
            }
          }
        }
      }
    }
  }
}

Code from IDA. IDK what give last param, i call him must_be_true, set to true