Index: ai_char_normal.cpp
===================================================================
--- ai_char_normal.cpp	(revision 1997)
+++ ai_char_normal.cpp	(working copy)
@@ -2213,14 +2213,25 @@
 					}
 
 					uint16 bonusDMG = 0;
+					bool bTHIncreased = false;
 					if(m_PChar->GetMJob() == JOB_THF && (!ignoreSneakAttack) &&
 						m_PChar->StatusEffectContainer->HasStatusEffect(EFFECT_SNEAK_ATTACK) &&
 						abs(m_PBattleTarget->loc.p.rotation - m_PChar->loc.p.rotation) < 23)
 						{
 							bonusDMG = m_PChar->DEX();
-							if(rand()%100 < 4) Monster->m_THLvl +=1;
-						}
+							if(rand()%100 < 4)
+							{
+								bTHIncreased = true;
+							}
 
+					}
+					else if(m_PChar->GetMJob() == JOB_THF)
+					{
+							if(rand()%100 < 1)
+							{
+								bTHIncreased = true;
+							}
+					}
 
 
 					//trick attack agi bonus for thf main job
@@ -2261,6 +2272,14 @@
 						m_PChar->addHP(-0.1*m_PChar->health.hp);
 					}
 
+					if(bTHIncreased && damage > 0 && Monster->m_THLvl < 12)
+					{	
+						Monster->m_THLvl +=1;
+						Action.submessageID = 603;
+						Action.flag = 1;
+						Action.subparam = Monster->m_THLvl;
+						Action.subeffect = SUBEFFECT_NONE;
+					}
 					charutils::TrySkillUP(m_PChar, (SKILLTYPE)PWeapon->getSkillType(), m_PBattleTarget->GetMLevel());
 					zanshin = false;
 				}