Here is full code.

global class foreignCompanies Implements Schedulable
            {
                       global void execute(SchedulableContext sc)
                        {
                                    sendmail();
                        }
                        public void sendmail()
                        {
                          string c ;
                          List<Account> acclist = [Select id,Name,BRN_UEN_NRIC__c,CreatedDate,CreatedBy.Name from Account where Is_Foreign_Company__c=TRUE and record_type__c='Advertiser' order by createddate desc limit 1];
                            string header = 'Id ,Account Name,BRN/UEN/NRIC/Foreign ID,Created Date,Creator \n';
                            string finalstr = header ;
                            for(Account a: acclist)
                            {     
                                   c = a.Name.replace(',',' '); 
                                   string recordString = a.id+','+c+','+a.BRN_UEN_NRIC__c+','+a.CreatedDate+','+a.CreatedBy.Name+'\n';
                                   finalstr = finalstr +recordString; 
                            }
                            finalstr = finalstr.replace('null','');
                           
                             Datetime dateTimetemp = System.now();
                            Date dateTemp = Date.newInstance(dateTimetemp.year(),dateTimetemp.month(),dateTimetemp.day());
                            String x=dateTemp.format();
                           
                             Map<String,ForeignCompany__c> mapRecipients =  ForeignCompany__c.getAll();
                             List<String> arrytoAddresses = new List<String>{};
                             List<String> arryccAddresses = new List<String>{};
                            
                             for(ForeignCompany__c objRecipient : mapRecipients.values()){
                             system.debug('+++'+objRecipient.To__c);
                             if(objRecipient.To__c==true)
                             arrytoAddresses.add(objRecipient.Email__c);
                             else
                             arryccAddresses.add(objRecipient.Email__c);
                             }
                            system.debug('+++'+arrytoAddresses);
                             system.debug('+++'+arryccAddresses);
                           
                            Messaging.EmailFileAttachment csvAttc = new Messaging.EmailFileAttachment();
                           
                            blob csvBlob = Blob.valueOf(finalstr);
                            string csvname= 'Foreign Companies List.csv';
                            csvAttc.setFileName(csvname);
                            csvAttc.setBody(csvBlob);
                            csvAttc.setContentType('text/csv;charset=UTF-8');
                            //csvAttc.ContentType = 'text/csv; charset=UTF-8';
                          
                           
                            Messaging.SingleEmailMessage email =new Messaging.SingleEmailMessage();
                            String subject ='Foreign Companies List '+x;
                            email.setCharset('UTF-8');
                            email.setSubject(subject);
                            email.setToAddresses(arrytoAddresses);
                            email.setCcAddresses(arryccAddresses );
                            email.setPlainTextBody('This is a system generated daily report of Foreign Companies');
                            email.setFileAttachments(new Messaging.EmailFileAttachment[]{csvAttc});
                            Messaging.SendEmailResult [] r = Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email});
                 
                        }
            }

Let me know where to add Encoding UTF-8.  In order to open in some text editor user have to save the csv from the email.
But users should be able to open directly from email i.e csv file.